The development of the perifused fat cell system allows for the determination of lipolytic rates over very short periods of time. Thus, the rate at which epinephrine stimulates lipolysis and the rate at which lipolysis returns to basal following removal of the hormone can be studied. With this project the perifused fat cell system will be used to study the control of lipolysis. The relationship among hormone binding, cyclic AMP levels, protein kinase activity, hormone-sensitive lipase, and glycerol production will be determined as a function of time and of dose of epinephrine. These relationships will be determined following the initiation and termination of an epinephrine infusion in the absence and presence of antilipolytic agents such as insulin and prostaglandins.